I was trying to fix this, but I guess nothing worked.
I tried to put the text in a div and then tried to remove the filter but it didn't work. Here is my HTML and CSS code:
.welcome {
  background-image: url('code.jpg');
  -webkit-filter: brightness(70%);
  filter: brightness(70%);
}
.head {
  filter: none;
  color: white;
}
<div class="welcome">
  <center>
    <h1 class="head">Relux OS</h1>
    <p class="head">Have the greatest experience.</p>
  </center>
</div>